Whoa! That adds up to a lot of itchy, flaky skin complaints that could be linked to a lack of zinc.

Zinc is a workhorse nutrient that's involved in almost every biochemical reaction in your body, but it's especially important for skin-cell renewal. Zinc isn't hard to find -- shellfish, lean ham, beef, and lamb are full of it (vegetarians need to work a bit harder to get enough). But as the list above shows, it's easy to throw off zinc levels. A lot of things can either drain the body's supply (breastfeeding) or interfere with zinc's absorption (almost everything else; calcium supplements alone can cut it in half).

So how much zinc do you need, and how can you get enough to keep your skin's RealAge young? The recommended daily amount is 15 mg, which can be found in most multivitamins. But aim to get a little more, especially if you're dealing with anything on the list above. Good sources:

Oysters: They're the all-stars; depending on the type, they can run from 16 mg a half dozen to 40 mg or more, but they're hardly a staple food.

Fortified breakfast cereals: They can be terrific; for instance, a cup of Cheerios has 15 mg.

Eating several of the following every day: meat, chickpeas, lentils, dairy foods, and nuts. With a good mix of these, it's easy to get your daily dose.

Just don't go overboard. Getting more than the upper limit of 40 mg can cause heart-healthy good HDL cholesterol to plummet and can throw off your immune system.

That said, if summer sun and hot weather has left you with persistent dry-skin patches, try rubbing on a zinc cream. No, not the white nose goop lifeguards swear by. We mean diaper-rash creams like Vusion. "The zinc oxide in them really helps," says Manhattan dermatologist Jeffrey Weinberg, MD, "probably because it makes such a terrific barrier against moisture loss and protects skin from external irritants."